1. Field
The present specification describes an IC-tag read-write apparatus, and more particularly to an IC-tag read-write apparatus capable of performing a stable radio data communication with an IC tag.
2. Discussion of the Background
A typical structure of a background IC (integrated circuit) tag read-and-write apparatus 100 is illustrated in FIG. 1. The background IC-tag read-and-write apparatus 100 communicates with a plurality of IC tags including an IC tag 110 and an IC tag 120 by performing a data read and write operation using radio waves. The background IC-tag read-write apparatus 100 of FIG. 1 includes an antenna ANTa, an oscillating circuit (OSC) 101, a controlling circuit (CONT) 102, and a signal modulating circuit (MOD) 103. The IC tag 110 of FIG. 1 includes an antenna ANTb1 and a signal modulating circuit (MOD) 111. The IC tag 120 of FIG. 1 includes an antenna ANTb2 and a signal modulating circuit (MOD) 121.
The oscillating circuit 101 generates and outputs a carrier wave to perform a radio communication with the IC tags such as the IC tags 110 and 120. The frequency of the carrier wave is generally 13.56 MHz. For some special applications, it may be lower in a range of from 120 KHz to 500 KHz, or even a microwave of 2.4 GHz.
In a case of writing data into the IC tag 110, for example, the background IC-read read-write apparatus 100 conducts the operations in the following manner. The controlling circuit 102 receives the carrier wave from the oscillating circuit 101 and performs an input and output control of a data signal to be superimposed on the carrier wave. The signal modulation circuit 103 receives the carrier wave and data signal output from the controlling circuit 102 and conducts a signal modulation to the carrier wave in accordance with the data signal. The modulated signal is transmitted by radio through the antenna ANTa. The IC tag 110 receives the radio signal sent from the background IC-tag read-write apparatus 100 and demodulates the received signal with the signal modulation circuit 111.
In a case of reading data from,the IC tag 110, for example, the background IC-read read-write apparatus 100 conducts the operations in the following manner. The background IC-tag read-write apparatus 100 sends a select command and a read command to both IC tags 110 and 120. The select command is to select the IC tag 110, for example, and the read command is to instruct the selected IC tag to output the data desired. Upon receiving the select and read commands, the IC tag 110 is activated and modulates the carrier wave with the signal modulation circuit 111. Then, the IC tag 110 sends the data requested by the read command and transmits by radio the carrier wave together with the requested data through the antenna ANTb1. The background IC-tag read-write apparatus 100 receives the radio signal with the antenna ANTa, demodulates the received signal, and retrieves the data requested. In this event, the IC tag 120 is not selected and is not activated, so that it does not output the data desired by the read command. Accordingly, to read data from the IC tag 120, for another example, the background IC-tag read-write apparatus 100 needs to send a select command to the IC tag 120 before the read command so as to select the IC tag 120.